JVC DVD Power board

[tmcw]

Trying to troubleshoot the power board from the following unit:

JVC DVD-Player
Model No. XV-N320B
AC 230V 50Hz 11W

I found a service manual at elektrotanya, I've attached the page with the power board schematics for convenience if anyone thinks they can help me.

The unit isn't powering up when plugged in.

There is an obviously bulged cap at C983 (Samxon GF (M) 470uF 10V), but I haven't replaced that yet, as I'm trying to work through the power board checking as much as I can before I get to that cap.

I tested the bridge rectifier at D903, and it tested good.

From the schematic, it looks like the first place I can check voltages is at IC901. There are 4 voltages there that I should be able to check. I get AC voltage reading of approx. 10V on all 4 output pins of IC901.

Can I assume that the chip is at fault then, or should I consider anything else (like the cap at C907)? Is there anything I can check/measure prior to IC901?

The bulging cap at C983 shouldn't affect the voltages back here, should it? Is it more likely that the bulging cap is a symptom on the high voltages at IC901?

Also, should I be testing the power board with the DVD drive unit and digital board connected? I figured on testing the power board without anything connected initially at first. I understand that the unit isn't worth much, the overvoltage has possibly blown the other boards, but I'm just messing with this to see if I can learn.

[retiredcaps]

Re: JVC DVD Power board

I get AC voltage reading of approx. 10V on all 4 output pins of IC901.

I believe the voltage at IC901 should be measured as DC volts.

[tmcw]

Re: JVC DVD Power board

Should it?

I was using an autorange meter when I was testing it, and the meter couldn't get a value on DC. I could get the 10V on AC reading though.

I'll get another meter and test it again.

[Th3_uN1Qu3]

Re: JVC DVD Power board

Replace the cap first, it will interfere with voltage measurements.

[tmcw]

Re: JVC DVD Power board

Ok, tested again on DCV, and the voltage seems to be slowly increasing all the time, from about -1 approaching 0, taking a long time to go towards 0 though.

I also tested the outputs of PC901, and getting good 3.1V and 2.1V respectively there, though the other side (for 5.6v and 4.3v) show a similar increasing voltage as for the outputs of IC901.

[tmcw]

Re: JVC DVD Power board

Replace the cap first, it will interfere with voltage measurements.

Ok, will do, only have a cheapie "Suntan" 25V cap of the 470uF value, but I'll give it a go

[tmcw]

Re: JVC DVD Power board

Ok, I've changed the C983, and also changed the C954, as it was the same value and type of capacitor.

The 4 outputs on IC901 still do the same increasing voltage towards 0V.

The 2 outputs on PC901 are still about 3V and 2V.

The 3.3V at pins 12 and 13 on CN901 are ok (thanks to C983).

The 9V expected at pins 2 and 3 on CN901 are about 13.3V.

The 5.7V expected at pins 6 and 7 on CN901 are about 8.3V. Was hoping the change of C954 would have taken care of this.

Is there any way of testing the associated choke coils and diodes in-circuit?

Or should I be looking at the transformer?

[retiredcaps]

Re: JVC DVD Power board

A clear focused picture of the board using manage attachments would help. Please do not post inline.

[tmcw]

Re: JVC DVD Power board

Hope these are good enough. It's night-time here, so using artificial light.

Also uploaded a block diagram from the service manual.

[retiredcaps]

Re: JVC DVD Power board

The 9V expected at pins 2 and 3 on CN901 are about 13.3V.

The 5.7V expected at pins 6 and 7 on CN901 are about 8.3V. Was hoping the change of C954 would have taken care of this.

These voltages could be fine without a load. At this point, I wolud reassemble everything and try out the player.

[kc8adu]

Re: JVC DVD Power board

i would replace all the secondary caps.
some of the small ones look like they may have leaked a bit.could be flux too.